Federal Emergency Management Agency (FEMA) Standardized Awareness Practice Test

A negative blast pressure phase is characterized by a vacuum or suction effect, which occurs after the initial explosion. During an explosion, the rapid release of energy results in a significant pressure wave moving outward. Once this wave passes, the surrounding air rushes back in to fill the void left by the explosion, creating a negative pressure or suction effect.

This characteristic is crucial in understanding how explosions interact with their environment, particularly in the aftermath where structural damage can be exacerbated by this vacuum. It may lead to further risks, such as causing debris to become airborne or drawing materials towards the center of the blast, posing additional hazards to anyone nearby. Recognizing the implications of this negative phase is essential for emergency response and safety protocols.